DataSet 数据集的使用

语法: 

public static DataTable ExecuteTable(string sql)
        {
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(sql, conn);
                SqlDataAdapter adapter = new SqlDataAdapter(cmd);
                DataSet ds = new DataSet();
                adapter.Fill(ds);
                return ds.Tables[0]; 
            }
        }

使用: 在窗体加载的时候调用 ExecuteTable

private void FrmAddStudent_Load(object sender, EventArgs e)
{
    string sql = "select * from StudentClass";
    DataTable dataTable = SqlHelper.ExecuteTable(sql);
    //向集合第一个位置插入一条数据
    DataRow dr = dataTable.NewRow();
    dr["ClassId"] = 0;
    dr["ClassName"] = "请选择班级";
    dataTable.Rows.InsertAt(dr, 0);
    this.comboBox1.DataSource = dataTable;
    this.comboBox1.DisplayMember = "ClassName";
    this.comboBox1.ValueMember = "ClassId";
}

展示: